Rob N 72e4996a54 bdev_discard_supported: understand discard_granularity=0 ... Kernel documentation for the discard_granularity property says: A discard_granularity of 0 means that the device does not support discard functionality. Some older kernels had drivers (notably loop, but also some USB-SATA adapters) that would set the QUEUE_FLAG_DISCARD capability flag, but have discard_granularity=0. Since 5.10 (torvalds/linux@b35fd7422c) the discard entry point blkdev_issue_discard() has had a check for this, which would immediately reject the call with EOPNOTSUPP, and throw a scary diagnostic message into the log. See #16068. Since 6.8, the block layer sets a non-zero default for discard_granularity (torvalds/linux@3c407dc723), and a future kernel will remove the check entirely[1]. As such, there's no good reason for us to enable discard when discard_granularity=0. The kernel will never let the request go in anyway; better that we just disable it so we can report it properly to the user. 1. https://patchwork.kernel.org/project/linux-block/patch/20240312144826.1045212-2-hch@lst.de/ Sponsored-by: Klara, Inc. Sponsored-by: Wasabi Technology, Inc. Signed-off-by: Rob Norris <rob.norris@klarasystems.com> (cherry picked from commit b181b2e604)		2024-04-19 10:19:53 -07:00
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freebsd	dmu: Allow buffer fills to fail	2024-02-20 15:53:02 -08:00
linux	bdev_discard_supported: understand discard_granularity=0	2024-04-19 10:19:53 -07:00